Geology of Ore Deposits

, Volume 56, Issue 8, pp 637–643 | Cite as

Ferroindialite (Fe2+,Mg)2Al4Si5O18, a new beryl-group mineral from the Eifel volcanic region, Germany

  • N. V. Chukanov
  • S. M. Aksenov
  • I. V. Pekov
  • B. Ternes
  • W. Schüller
  • D. I. Belakovskiy
  • K. V. Van
  • G. Blass


A new mineral, ferroindialite, a Fe2+-dominant analog of indialite, has been found in a pyrometamorphosed xenolith of pelitic rock hosted in alkaline basalts. Associated minerals are phlogopite, sanidine, sillimanite, pyroxenes of the enstatite-ferrosilite series, wagnerite, fluorapatite, tridymite, zircon and almandine. Ferroindialite forms brown-purple to gray with a violet-blue tint short prismatic or thick tabular hexagonal crystals up to 1.5 mm in size. The new mineral is brittle, with a Mohs’ hardness of 7. Cleavage is not observed. D meas = 2.66(1), D calc = 2.667 g/cm3. IR spectrum shows neither H2O nor OH groups. Ferroindialite is anomalously biaxial (−), α = 1.539(2), β = 1.552(2), γ = 1.554(2), 2V meas = 30(10)°. The mineral is weakly pleochroic, ranging from colorless on X to pale violet on Z. Dispersion is weak, r < v. The chemical composition (electron microprobe, mean of five point analyses, wt %) is as follows: 0.14 Na2O, 0.46 K2O, 4.95 MgO, 1.13 MnO, 12.66 FeO, 2.64 Fe2O3, 30.45 Al2O3, 47.22 SiO2, total is 99.65. The distribution of total iron content between Fe2+ and Fe3+ was carried out according to structural data. The empirical formula of ferroindialite is: (K0.06Na0.03)(Fe 1.12 2+ Mg0.78Mn0.10)Σ2.00(Al3.79Fe 0.21 3+ )Σ4.00Si4.98O18. The simplified formula is: (Fe2+,Mg)2Al4Si5O18. The crystal structure has been refined on a single crystal, R = 0.049. Ferroindialite is hexagonal, space group P6/mcc; a = 9.8759(3), c = 9.3102(3) Å, V = 786.40(3) Å3, Z = 2. The strongest lines in the X-ray powder diffraction pattern [d, Å (I, %) (hkl)] are: 8.59 (100) (100), 4.094 (27) (102), 3.390 (35) (112), 3.147 (19) (202), 3.055 (31) (211), 2.657 (12) (212), 1.695 (9) (224). The type specimen of ferroindialite is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4400/1.


Cordierite Tourmaline Sillimanite Fluorapatite Unit Cell Dimension 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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© Pleiades Publishing, Ltd. 2014

Authors and Affiliations

  • N. V. Chukanov
    • 1
  • S. M. Aksenov
    • 2
  • I. V. Pekov
    • 3
  • B. Ternes
    • 4
  • W. Schüller
    • 5
  • D. I. Belakovskiy
    • 6
  • K. V. Van
    • 7
  • G. Blass
    • 8
  1. 1.Institute of Problems of Chemical PhysicsRussian Academy of SciencesChernogolovka, Moscow oblastRussia
  2. 2.Institute of CrystallographyRussian Academy of SciencesMoscowRussia
  3. 3.Faculty of GeologyMoscow State UniversityMoscowRussia
  4. 4.MayenGermany
  5. 5.AdenauGermany
  6. 6.Fersman Mineralogical MuseumRussian Academy of SciencesMoscowRussia
  7. 7.Institute of Experimental MineralogyRussian Academy of SciencesChernogolovka, Moscow oblastRussia
  8. 8.EschweilerGermany

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